Many studies have been widely carried out to develop light emitting device so far. The light emitting device includes an LED chip and a phosphor. (e.g., Reference 1) The phosphor is employed as a wavelength conversion member which is excited by a light emitted from LED chip and radiates a light of color different from the luminescent color of the LED. The light emitting device is capable of radiating a light of mixed-color which is different from the luminescent color of LED, when including the phosphor and the LED chip. For example, the light emitting device is commercially available as a white-colored light emitting device (generally referred to as a white-color LED), in which the LED chip emitting blue-color or UV light is combined with the phosphor to give white-color light (white-color luminescent spectrum).
The reference 1 discloses one example of light emitting device shown in FIGS. 11 and 12. The light emitting device discloses an LED chip 110. a mounting substrate 120 mounting the LED chip thereon, an optical member (an output-magnifying portion) 160 shaped like convex lens covering the LED chip, and a dome-shaped color conversion member (wavelength conversion member) 170 containing a phosphor. The color conversion member is secured to the mounting substrate 120 to cover the optical member 160 therewith. The phosphor is excited by a light emitted from the LED chip and radiates a light of color different from the luminescent color of the LED chip 110.
In the light emitting device shown in FIGS. 11 and 12, the mounting substrate 120 is provided at its top surface with a recess 123 which accommodates an LED chip 110 and a portion of the optical member 160 therein. In this light emitting device, the LED chip 110 is flip-flop mounted within the recess 123 of the mounting substrate 120. In this light emitting device, the LED chip 110 in the recess 123 of the mounting substrate 120 is encapsulated with an encapsulating resin 150.
In the light emitting device shown in FIGS. 11 and 12, the mounting substrate 120 is provided at its top surface with an annular groove 129 which surrounds entirely the periphery of the recess 123. The annular groove 129 is designed to store therein an extra encapsulation resin which overflows outside in the process of filling the recess 123 with the encapsulating resin 150. The color conversion member 170 is secured at its bottom rim to engage with the annular groove 129, by means of the encapsulating resin filled within the annular groove 129.
In fabrication of the light emitting device shown in FIGS. 11 and 12, the annular groove 129 in the top surface of the mounting substrate 120 allows the encapsulation resin to be sufficiently injected into the recess 123 such that the encapsulating resin 150 is free from void-generation.
In the process of flip-flop mounting the LED chip 110 within the recess 123, electrodes of the LED chip 110 is positioned opposite to an inner bottom of the recess 123 of the mounting substrate 120. Then, the optical member 160 shaped like convex lens is disposed to cover the LED chip 110 therewith. In this process, it is difficult to set an optical axis of the optical member 160 to be matched with both that of the LED chip 110 and that of the color conversion member 170. Besides, the light emitting device made in this process may decrease a light output, because a portion of the light leaking from a lateral face of the LED chip 110 is possibly absorbed into the mounting substrate 120, rather than directed outwardly.
In the light emitting device, the mounting substrate 120 is provided at its top surface with an annular groove 129. The mounting substrate 120 is provided at its bottom surface with a patterned conductor (not shown) which supplies electricity. When being configured to mount thereon the light emitting device acting as a light source of luminaire, the mounting substrate 120 needs to be disposed on a circuit substrate before accommodated in the main body of luminaire. But, the light emitting device in this configuration may suffer from an excessive thermal resistance between a light emitting part of the LED chip 110 and main body. As a result, this light emitting device luminaire needs to be controlled to receive a limited input electric power to the LED chip 110 such that a junction temperature of the LED chip 110 is kept below the maximum of junction temperature. Namely, this light emitting device may not give a high light output.
In the light emitting device shown in FIGS. 11 and 12, the mounting substrate 120 can be provided at its top surface with a patterned conductor. However, in the process of disposing the color conversion member 170 securely to the mounting substrate 120 in this configuration, an extra encapsulation resin overflowing from the groove 129 may flow to electrodes which are exposed outside of the color conversion member 170, eventually causing a poor solder connection.
In fabrication of the light emitting device shown in FIGS. 11 and 12, the encapsulation resin needs to be supplied into the recess 123 of the mounting substrate 120 engaging with a portion of the optical member 160 which is larger in external dimension than the LED chip 110. This light emitting device may suffer from void-generation inside the encapsulation resin 150, possibly giving a lowered light output.
References 2 and 3 disclose examples of light emitting devises shown in FIGS. 13 and 14, respectively. In each of the light emitting devices, the mounting substrate 120 is provided at its top surface with a gate 127. The gate 127 acts to prevent an extra encapsulation resin from flowing outside, in the process of encapsulating the LED chip 110 and bonding wires 114 (not shown in FIG. 13) with the encapsulation resin 150. The gates 127 in FIGS. 13 and 14 are formed of a black resist and an epoxy resin, respectively.
In the light emitting devices in FIGS. 13 and 14, the encapsulation resin 150 may extend over the gate 127, although the gate 127 acts to define an external dimension of the encapsulation resin 150.    Reference 1: Japanese unexamined patent publication 2005-158949 (paragraphs 0016 to 0017, FIGS. 3 and 4)    Reference 2: Japanese unexamined patent publication 2003-345268 (paragraphs 0009 to 0015, FIG. 5)    Reference 3: Japanese unexamined patent publication 2003-152226 (paragraphs 0018 to 0019, FIG. 3)